Thursday, May 6, 2010

vim Productivity

I use vim. Not because I think it is inherently superior to emacs or any other full-featured editor/IDE, but because I learned it first. A fellow vim user and friend of mine tried emacs out for about a semester+ and his experience was that they are roughly equivalent after learning how to use each, so I stick with vim. The only real difference between the two is the command syntax

Through working on various projects, I have gathered a few tricks, tips, and features to improve my productivity while using vim. The rest of this post is a semi-tutorial and repository of my vim usage.

Built-ins:

.vimrc

Modes

Cut-Paste

Find-Replace

Jumping Around

Split

Auto-Format

Shell commands

Plug-ins:

Latex-suite

Cscope

changelog

.vimrc
One of the most useful things to learn (or at least do) with vim is to get a good .vimrc. The .vimrc is read from your home directory when you open vim, and it can be used to override and set many options to customize your vim environment. Look around online for vimrc options and settings, here is a sample vimrc that is close to what I use:

" Use Vim settings, rather then Vi settings (much better!). " This must be first, because it changes other options as a side effect.
set nocompatible

" allow backspacing over everything in insert mode
set backspace=indent,eol,start

" change spacing for tabbing and autoindent
set tabstop=2 "number of columns to display in a tab
set shiftwidth=2 "how many columns to indent with autoindent
set expandtab " inserts spaces instead of tab
set autoindent " always set autoindenting on
set smartindent

set nobackup " do not keep a backup file, use versions instead
set history=50 " keep 50 lines of command line history
set ruler " show the cursor position all the time
set showcmd " display incomplete commands
set incsearch " do incremental searching

" Don't use Ex mode, use Q for formatting
map Q gq

" Switch syntax highlighting on, when the terminal has colors
if &t_Co > 2 || has("gui_running")
syntax on "set background=dark" use with dark terminal windows."set hlsearch "highlight the last used search pattern
endif

" Only do this part when compiled with support for autocommands.
if has("autocmd")

" Enable file type detection. " Use the default filetype settings, so that mail gets 'tw' set to 72, " 'cindent' is on in C files, etc. " Also load indent files, to automatically do language-dependent indenting.
filetype plugin indent on

A lot of the options in the .vimrc help with formatting. My options provide for tabs to be two white space characters. This also turns on syntax highlighting, indentation, and breaking hard links, which I mentioned in my previous post about versioning work.

Modes
Vim has a number of modes that change how you interact with the editor. The modes that I use are normal, insert, command-line, and visual. There are some other modes, but I avoid them. Normal mode is the mode you start in, and is mainly useful for navigating through text and issuing simple commands. Insert mode is entered by pressing i from normal mode, and is used for editing text. Command-line mode is entered by pressing the colon key, :, while in normal mode. You need to use command-line mode to save and to quit vim, for example, while in normal mode pressing :wq will save and quit, :q! will quit without saving changes; the help menu is also accessed using :help. Visual mode is entered by pressing v from normal mode, and I will explain some of its uses in the next paragraph.

To enter visual mode, hit the esc key (to enter normal mode) and then press v. Then you can move your cursor around with the arrow keys to highlight text. Visual mode is useful for making controlled changes within your text. To get back to editing, hit esc and then press i to enter insert mode. With visual mode, you can use vim commands to operate on the text that you highlight. Simply highlight the region of text you want to search and replace in, and then hit :, which will bring up a command that is automatically scoped to the range you have highlighted, which looks like this :'<,'> . Some of the remaining sections will discuss ways to use visual mode for a more advanced vim experience.

Cut-Paste
Probably one of the more important features of an editor is the ability to move chunks of text around efficiently. Cutting and pasting is easy enough in vim. First let's see how to copy text. To copy a line of text, enter normal mode and press yy. This will "yank" the current line of text. To paste what you yanked, enter normal mode and press p, which will paste the yanked line wherever the cursor is located.

You can also cut a line of text, enter normal mode and press dd, which deletes the line and saves it in vim's clipboard. You can also yank or delete two lines, enter normal mode and press either:

d [down arrow OR up arrow]

y [down arrow OR up arrow]

These two commands will cut or copy (respectively) the current line and the next or previous (respectively) line. Then you can paste the two lines anywhere you like. It is also possible to cut/copy multiple lines. Do this by entering command mode Typically when I need to get more than two lines I always use visual mode.

Enter visual mode and then highlight the text you want to cut/copy. While still in visual mode, press d or y to cut or copy the highlighted text -- you will be returned to normal mode, and can paste your text where you need. This method allows you to control precisely which text to cut or copy, you can select parts of lines and even just part of a single line, or a single word for example. The only real limitation is that you can only highlight contiguous regions, at least I haven't learned how to cut multiple selected regions at once. I also use this method to just delete text that is no longer needed by highlight and pressing d, without ever pasting the clipboard buffer contents anywhere.

One limitation to this method of copy and paste is that the vim clipboard buffer only works in a single instance of vim. This means with the above method you cannot copy/paste between vim instances, or between any other program and vim. Also, with auto-indent and other features enabled, pasting with the terminal window (which copies/pastes the system clipboard) or mouse buffer can lead to some very messy formatting issues. I recently learned how to get around this limitation, and can now copy and paste nicely between vim and the system or mouse clipboards.

How to copy and paste between vim instances
To copy a line of text from vim into the system or mouse clipboards, enter normal mode and press "+yy or "*yy respectively.

You can also use visual mode to copy the highlighted text to the system and mouse clipboards. In visual mode, highlight the text you want to copy, and press "+y or "*y. Cutting text works identically, but with d instead of y. You can also paste from either clipboard from normal mode with "+p or"*p.

These two paste commands work for text copied in other applications or for the text currently highlighted by the mouse, and using the p command instead of the terminal (ctrl+shift+v) or mouse paste (middle mouse click) will prevent vim from attempting to automatically format the pasted text.

I have had some trouble with this in Fedora, but it works well with Ubuntu.

Find-Replace
There's almost always a need to do a little search, and maybe even some replace. Find in vim is easy, just hit / and then type what you want to find. To do find and replace, you use the : to enter command mode (first press esc if you are in insert mode; commands can be entered directly in visual mode). From normal mode, pressing :s/find/replacewill replace the first instance of find with replace in the current line. To replace every instance of find with replace in the current line, you need to add a /g to the end :s/find/replace/g

Usually what you want to do is to replace every instance in the entire file. Do this by adding a range specifier before the s, for example :%s/find/replace/g

You can also do find replace over a range, for example between lines 1 and 100 you would enter :1,100s/find/replace/g

This is really easy to do if you use visual mode. As explained before, simply highlight a region and press :, then s/find/replace/g.

Jumping Around
Despite not supporting a mouse, after learning a few tricks it is exceedingly simple to navigate through text. To jump to a specific line number, simply enter the line number in command mode, for example :42 will jump to line number 42. You can also jump to relative line numbers, for example :-42 or :+42 will jump back or forward 42 lines respectively. And if you don't know an exact line number, you can also jump to an approximate line number, for example pressing 42% in normal mode will place your cursor past 42% of the file.

There are also commands to jump to specific places in a file. For example, entering gg in normal mode will jump to the start of the file, and entering G will jump to the end of the file. There are also useful commands to move within a single line: pressing ^ will move your cursor to the start (first non-whitespace character) of the current line, and pressing $ will move your cursor to the end of the line. There are a lot of other ways to efficiently move around, but these are the commands I use most often.

Split
Quite often I work on one file and want to reference another file. Using the split command lets me open multiple files in the same terminal and same instance of vim. For example, entering :split foo.c will open the file foo.c (assuming it is in the same directory in which vim started) in a split portion of the current window. You can open any file by passing relative or absolute paths to the split command.

Window commands begin by first pressing ctrl-w and another letter. To cycle between open windows, use ctrl-w w. You can control the window to move to, with horizontal splits use ctrl-w j (or up arrow) or ctrl-w k (or down arrow) to move to the window above or below your current window. :vsplit will create a vertical split. I almost always use regular split with a file name and cycle through windows with ctrl-w w.

I have also previously learned how to use tab pages, which lets you open multiple files in tabs, where each file takes up a whole window. To open a file foo.c in a new tab, use :tabeditfoo.c, which works like split except it creates a tab. You can also open the same file as you are currently editing with :tab split. To cycle through the tabbed windows use gt in normal mode, or gT to go to the previous tab.

Auto-Format
Before I learned to use "+p and "*p to paste, I would often paste code and it would be really badly formatted. With the autoindent options set in the .vimrc, I can easily reformat the text. A single line can be formatted by pressing == in normal mode, but that is usually not sufficient. I almost always use visual mode to highlight the text I want to format, and then press =. You can also reformat the entire file, by going to the start of the file with gg then pressing = followed by G.

Shell commands
From the vim command-line, you can also issue arbitrary commands to the underlying shell using the ! operator. For example, :!pwd will print the current working directory and prompt to return to editing. You can also pass data to another program like using a pipe, for example you can highlight a range and then sort the lines by using :'<,'>!sort; note that the output of the external program will replace the input. More complicated expressions can also be constructed, although I don't use this feature of vim very often.

Latex-suite
One of the first plug-ins that I ever tried is the latex-suite; Ubuntu provides a package called vim-latexsuite. Although it has a slight learning curve, it is pretty easy to pick up and use. Some of its nicer features that I use are templates, citation completion, and folding for latex. One annoyance with the latex-suite is the macro expansion, which occasionally expands text that I don't want expanded. For this, I can set b:Imap_FreezeImap to 1 to pause it for the current window, or set g:Imap_FreezeImap to 1 in the .vimrc to turn it off completely.

Templates are LaTeX files that have placeholders for customizing the file with your data. I typically just use the templates to start new projects and replace all of the placeholders with blanks, but there is some support for moving through the placeholders. Citation completion makes it easy to insert citations by simply typing \cite{ and then starting the citation completion. Folding is a way to hide text, which can make it quicker to scan through a file to find a section that you want to work on. Folds are opened with the command zo and closed with zc. Latex suite takes care of creating the folds for you.

I tend to use gvim with latex-suite, since the GUI options are nice and I don't have to remember the extra key bindings.

Cscope
I haven't used Cscope much, but it is a nice tool for moving through a source code tree quickly. Cscope is especially useful for finding function or symbol definitions and uses. I learned how to use it with vim from an online tutorial. One of the keys to successfully using Cscope is to generate the database it uses for searching for symbols. What you provide to Cscope is a file containing a list of all the files for it to include in the database. I use the find command to generate this list. For example, to generate the Cscope database for RTEMS I use the following commands (with $r equal to the top level of the rtems source directory, and $R is the parent of $r):

This will create the cscope.out database file. If you have the cscope_maps.vim file in a good location, then the only other thing to do is to show vim where to find the cscope.out file. I typically use Cscope to find files and to search for symbol and function definitions. Vim's command-line mode can be used to issue Cscope commands, for example :cs find f foo.c will search for the file foo.c and either open it if it is unique in the database or give you a menu of files named foo.c to choose from. There are also key bindings in the cscope_maps.vim file that define some useful shortcuts. The one I use most often is to put my cursor on a symbol (e.g. a struct type or function name) and then hit ctrl-\ s or ctrl-@ s (control + spacebar + s), which will display a list of all references to the symbol. I can select the one I want by typing in a number included with the list, and it will open in the same window (if I used ctrl-\) or in a horizontal split (if I used ctrl-spacebar). There are a lot of other ways to use Cscope -- the tutorial gives some, and the cscope_maps.vim file lists a few more.

changelog
One of the projects that I have been working on a lot recently is RTEMS. The RTEMS project uses Changelogs to track modifications to the source files. These files have a simple but strict format, and manually creating ChangeLog entries is tedious. Vim has plugin support for generating ChangeLog entries. Simply add this to your .vimrc:

I also found that the default behavior for the ChangeLog plugin is to merge all entries by the same user on the same day together in a single ChangeLog. I prefer to have separate entries for each time that I make a new entry, this way I can more easily track back the order of things that I change, and I also usually make an entry and then commit to my version control system. This means I need to change the plugin behavior. I did this by copying the default changelog.vim from the usual ftplugin directory, on my computer this is /usr/share/vim/vim72/ftplugin/changelog.vim, and I put the copy in ~/.vim/ftplugin/changelog.vim. Then I made some manual changes, but here is a diff:

Now whenever I make a change, I simply type \o in normal mode, which splits a window and opens the nearest ChangeLog file (searching up the directory tree) with a new entry for me to fill just the modifications I made. It automatically populates my name, email (from the .vimrc variable setting), the date, and the file name that I was editing. Then I can save and close the ChangeLog, and either resume editing or close the modified file if I'm done with my edits. Typically I only make ChangeLog entries right before closing a file, because then I will also be committing my changes to the version control system.

6 comments:

Today I found it necessary to add a new syntax highlighting, so that I can edit MoinMoin files in vim. First I downloaded http://www.vim.org/scripts/script.php?script_id=1459 to ~/.vim/syntax/moin.vim and then I added ~/.vim/filetype.vim with contents if exists("did_load_filetypes") finish endif augroup filetypedetect au! BufRead,BufNewFile *.wiki setfiletype moin augroup END

Note to self: To use the match of the search portion of a vim regex, place escaped parentheses around a part of the regular expression match and then use \# (e.g. \1, \2, \3) in the replace portion. This is useful to create a copy of text. For example,:%s/foo\(bar.*)/\1\1/will replace foobar* with bar*bar*

I was using python, and having a hard time with comment indentantion. I found this gem:

From the docs on smartindent:

When typing '#' as the first character in a new line, the indent for that line is removed, the '#' is put in the first column. The indent is restored for the next line. If you don't want this, use this mapping: ":inoremap # X^H#", where ^H is entered with CTRL-V CTRL-H. When using the ">>" command, lines starting with '#' are not shifted right.